OUTLINE: This is a dose escalation study of cladribine. Patients receive cladribine by continuous IV infusion 5 days a week for 4 weeks and undergo radiotherapy twice a day, beginning 3 hours after initiation of cladribine, 5 days a week for 4.5 weeks. Treatment continues in the absence of disease progression or unacceptable toxicity. Cohorts of 3-6 patients receive escalating doses of cladribine until the maximum tolerated dose (MTD) is determined. The MTD is defined as the dose preceding that at which 2 of 6 patients experience dose limiting toxicity. Patients are followed at 1 month, then every 3 months thereafter for survival.